Recently, I’ve noticed that many beginners still understand the KDJ indicator at a textbook level. In fact, this tool’s power in real trading is far beyond what most imagine, and the key lies in how to use it.

Let’s start with the basics: among the three lines of KDJ, the J line fluctuates the most frequently and is the most sensitive, the K line is next, and the D line is the most stable and lagging. This characteristic determines their respective uses. Many people set the KDJ parameters to the system default of 9, only to find that signals become too frequent, with buy and sell signals coming one after another, making it unusable. I’ve tried changing the parameters to values like 5, 19, and 25, and the results are much better—less frequent fluctuations and more reliable signals.

Regarding practical application, I pay most attention to the J value. When the J value stays above 100 for three consecutive days, a short-term top is often near; conversely, when it stays below 0 for three days, a bottom is likely forming. These signals are rare but highly reliable once they appear. Experienced traders around me are studying how to capture J value signals, which can be said to be the most ingenious aspect of the KDJ indicator.

Another detail worth noting: the range of K and D values is 0-100, but the J value can exceed 100 or drop below 0. For overbought and oversold conditions, D% above 80 is considered overbought, below 0 oversold; J% above 100 is overbought, below 10 oversold. The KD golden cross (K% crossing above D%) is a buy signal, while the death cross (K% crossing below D%) is a sell signal.

However, to be clear, the KDJ is fundamentally a short-term tool, best used in ranging markets. Once the market enters a strong uptrend or downtrend, the indicator tends to become dull, and signals become unreliable. At this point, you can switch to weekly KDJ parameters to look for medium-term opportunities. For example, if the weekly J line is below zero and turns upward with a bullish weekly candle, that’s a good buy point; conversely, if the weekly J line rises above 100 and turns downward with a bearish weekly candle, it’s a warning of a top.

Honestly, the KDJ indicator is often criticized, with some saying it’s not very useful. But that’s usually because the parameters aren’t tuned properly or the appropriate scenario isn’t understood. As long as you know how to flexibly adjust the KDJ parameters and combine it with market conditions, this indicator can still provide many valuable signals. The most important thing is patience—waiting for truly reliable signals rather than being led astray by frequent noise.